Peter Maslowski, “Military Intelligence Sources During the American Civil War: A Case Study,” “The Intelligence Revolution: A Historical Perspective,” Proceedings of the Thirteenth Military History Symposium, U.S. Air Force Academy, Colorado Springs, Colorado, October 12-14, 1988., edited by Lt. Col. Walter T. Hitchcock, USAF., Washington, D.C.: Office of Air Force History, United States Air Force.

NOTE: A Manual of Signals: For The Use Of Signal Officers In The Field, written by Albert Myer in 1864, can be seen on the Signal Corps Association Reenactors' Division website http://69.3.157.98/SCARD/signalmanual [external link disclaimer]